A similar idea was voiced a few days ago, specifically regarding Java libraries (http://fnords.wordpress.com/2010/09/24/the-real-problem-with...).
My response remains the same: Debian (or what-have-you) is but one distro among many, and those of us that treat such things as important but fundamentally commodity deployment platforms have no wish to spend our lives babysitting whatever package manager happens to be on the operating system we're using that month/year/whatever. Further, plenty of people have plenty of good reasons for deploying on Windows and OS X, so using tools that work well there make sense.
The priorities of the various linux distros aren't everyone else's priorities – which somehow seems to come as a galloping shock to some.
So, I guess I disagree. These tools provide a lot more than the usual package management.
To me it seems backwards to try to manage libraries globally when their use-cases are often already localized.
Somehow we got stuck with a critical mass of small-scale developers who never faced the nightmare of somehow keeping the right tarballs on hundreds of machines in different roles without good tools, so now we all get to relive it.